Sillito A M, Jones H E, Gerstein G L, West D C
Department of Visual Science, Institute of Ophthalmology, London, UK.
Nature. 1994 Jun 9;369(6480):479-82. doi: 10.1038/369479a0.
The function of the massive feedback projection from visual cortex to its thalamic relay nucleus has so far eluded any clear overview. This feedback exerts a range of effects, including an increase in the inhibition elicited by moving contours, but the functional logic of the direct connections to the thalamic cells that relay the retinal input to the cortex remains largely unknown. In contrast to its thalamic nucleus, the visual cortex is characterized by cells that are strongly sensitive to the orientation of moving contours. Here we report that when driven by moving oriented visual stimuli the cortical feedback induces correlated firing in relay cells. This cortically induced correlation of relay cell activity produces coherent firing in those groups of relay cells with receptive field alignments appropriate to signalling the particular orientation of the moving contour to the cortex. Synchronization of relay cell firing means that they will elicit temporally overlapping excitatory postsynaptic potentials in their cortical target cells, thus increasing the chance that the cortical cells will fire. Effectively this increases the gain of the input for feature-linked events detected by the cortex. We propose that this feedback loop serves to lock or focus the appropriate circuitry onto the stimulus feature.
到目前为止，从视觉皮层到其丘脑中继核的大量反馈投射功能尚未得到清晰的概述。这种反馈会产生一系列效应，包括增强由移动轮廓引发的抑制作用，但与将视网膜输入传递到皮层的丘脑细胞直接连接的功能逻辑在很大程度上仍然未知。与它的丘脑核不同，视觉皮层的特点是细胞对移动轮廓的方向高度敏感。我们在此报告，当由移动的定向视觉刺激驱动时，皮层反馈会在中继细胞中诱导相关放电。这种由皮层诱导的中继细胞活动相关性会在那些具有适合向皮层传递移动轮廓特定方向信号的感受野排列的中继细胞群中产生同步放电。中继细胞放电的同步意味着它们将在其皮层靶细胞中引发时间上重叠的兴奋性突触后电位，从而增加皮层细胞放电的可能性。实际上，这增加了皮层检测到的与特征相关事件的输入增益。我们提出，这个反馈回路用于将适当的神经回路锁定或聚焦到刺激特征上。
